FIELD OF THE INVENTION
The invention is directed to a method for monitoring the through-connect paths for information transmitted in the form of data bytes in digital time-division multiplex switching equipment.
Monitoring of the voice paths in time-division multiplex switching equipment is required in order to be able to recognize and localize faulty working of, in particular, that part of the switching equipment serving the purpose of a through-connection in order to either undertake an alternate switching of the affected parts until they are replaced, or to even see to an orderly abort of existing connections under certain circumstances.
Since, due to the time-division multiplex mode, the individual data bytes of the data stream incoming at a switching equipment unit change their time slot dependent on their allocation to a specific communication path, data protection techniques that extend over the totality of the data stream are not suitable; on the contrary, an error recognition that is individually associated to a voice path must be enabled.
A parity check of the data bytes conducted over the individual voice paths would not be adequate for an error recognition since, for example, misadjustment of the throughconnect paths cannot be recognized because the through-connected data bytes in such instances are in fact not the ones anticipated, but are inherently undisturbed.
In instances where the through-connect means of the switching equipment is redundant, whereby one half of the through-connect means is active in the normal case and the other half is available in a standby mode since the through-connect paths therein are likewise in fact set but the data stream likewise conducted over them is not forwarded, an additional test criterion can be acquired by comparing the two data streams. Given a lack of coincidence in case of error, further testing techniques must then be used to identify in which half of the two halves of the through-connect means the disturbance lies. When the malfunctioning half is subsequently temporarily taken out of operation until the error is eliminated, this additional test criterion no longer exists.
There would in fact be the possibility to provide the through-connect means more than just redundantly, in which case a parity check as the one testing technique could even be completely forgone and there is still the possibility of recognizing an error and the possibility of an alternate circuit even after a part of the through-connect means is taken out of operation after identifying an error in this part. Such a solution, however, involves a correspondingly high expense.